Automatic meter reading (“AMR”) is the technology of automatically collecting consumption, diagnostic, and status data from utility meters (e.g., water or energy metering devices such as gas or electric) and transferring that data to a central database at the system head end for billing, analyzing usage, and controlling the utility infrastructure. AMR and the Advanced Metering Infrastructure (AMI) that facilitates the associated utility systems communications and control are thus a particular example of the broader category of automated sensor data collection systems in which distributed monitors and sensors provide information that can be centrally collected and processed and used as a basis for implementing centralized or distributed system controls.
AMR technologies, as a representative of the greater class of automated sensor collection systems, have included handheld, mobile and fixed network technologies based on telephony platforms (wired and wireless), dedicated radio frequency (RF) collection systems, or powerline transmission. See generally http://en.wikipedia.org/w/index.php?title=Automatic_meter_reading &oldid=49046539. Of these approaches, RF data collection systems utilizing using licensed or un-licensed bands in the RF spectrum remains widely used for its effectiveness, ease of installation, reliability, relatively low cost, and independence from third-party networks.
Originally, this technology was developed to save utility providers the expense of periodic trips to each physical location to read a meter. Early systems used handheld reading devices that had to be hand-carried into the vicinity of each meter to conduct reads, thereby avoiding having to enter into the homes of customers. Subsequent technologies utilized vehicle-mounted readers that had the ability to drive through neighborhoods at posted speed limits while gathering data from meters, and eventually fixed networks in which reader devices are permanently installed to create a cellular-like AMR network able to read utility meters at greater frequency and provide commands and configuration updates to the utility meters in real time or near real time.
The utility meters in an AMR system are either interfaced with, or incorporate, an endpoint that obtains the meter's data, stores the data temporarily, and transmits the data to a reader. The simplest endpoints are transmit-only devices known as 1-way endpoints. These endpoints operate in a “bubble-up” regime in which their transmitters periodically wake up from a low-power sleep mode, transmit stored data, and return to their sleep mode. Typical bubble-up cycles are on the order of 15 seconds for AMR systems using vehicle-mounted readers, which is a time sufficiently short for each endpoint to remain within communication range of a moving reader. For hand-carried readers and fixed systems, the bubble-up cycle can be quite different.
Regardless as to the variation in bubble-up cycles, conventional fixed AMR systems that deploy 1-way endpoints must have the ability to handle massively duplicated data being transmitted repeatedly by numerous devices. Typically, duplicated data from repeated transmissions by 1-way devices are collected by the AMR system fixed receivers in which reconciliation of the duplicate data has been handled centrally at the system head end. Given the limited amount of data sent by each 1-way endpoint's transmissions, collection of the duplicated data and centralized reconciliation thereof, has been feasible.
Another type of transmit-only endpoint is known as a one-and-one-half-way (1.5-way) endpoint. The 1.5-way endpoint has a basic radio receiver circuit that is able to detect a specific signal called a wake-up tone. As its name implies, wake-up tones can be analog signals having a particular modulating tone; but can also be digital signals having a repeating pattern or predefined code. Instead of bubbling up and transmitting its data according to a recurring time schedule like a basic one-way device, the 1.5-way endpoint periodically activates its receiver momentarily to listen for a presence of a wake-up tone. If the wake-up tone is detected, the 1.5-way endpoint activates its transmitter circuit and sends its data. This mode of operation reduces collection system bandwidth requirements and saves energy in battery-powered endpoints because endpoints transmit only when a reader is within communication range.
The use of several distinct wake-up tones has been proposed for use as a limited set of predefined commands to 1.5-way devices. For instance one wake-up tone can be used to request the transmission of interval data, whereas another wakeup tone can be used to request transmission of a single reading. In some cases the wake-up signal may be addressed to an individual endpoint or to the endpoint's assigned group address. Still, 1.5-way endpoints lack the capability to initiate communications, and respond to, a complex instruction set (such as one that includes opcodes and variable operands, or re-configuration instructions). Thus, 1.5-way devices are regarded as primarily transmit-only endpoints.
More advanced endpoints known as two-way devices have a radio receiver in addition to a transmitter. The receiver allows the two-way endpoint to initiate communications connections as well as receive commands via the AMR system. This, in turn, enables AMR system operators to individually address specific two-way endpoints to request certain data, re-configure the two-way endpoint's operating modes, receive software or firmware updates, and the like. Two-way endpoints can also be used to send more advanced data, such as interval data for multiple sampling intervals, which requires longer message transmissions, or messages spanning multiple different transmissions. Since two-way communications allow the reader to request messages from endpoints, meter data as well as status information can be queried and provided in near-real-time. Also, the request for data can specify the particular data to be sent by the two-way endpoint, e.g., interval data at 15-minute intervals over the last 36 hours. This avoids having to collect this data over multiple separate transmissions (which places additional overhead requirements on the AMR system's bandwidth), storing large sets of duplicate or overlapping data for each endpoint for future data analysis needs, and having to deal with duplication-reconciliation of repeated messages.
Presently, AMR system operators are migrating their systems toward more advanced AMI systems using a fixed AMR infrastructure and self-organizing, autonomously-adapting two-way endpoints. Such systems use multi-hop communications in which endpoints act as originators of data, as well as routing devices that relay messages originated by other endpoints towards their destination. In these AMI systems, there is no pre-configuration of associations between endpoints; thus, devices must coordinate amongst themselves to form communication paths for the messages.
Even with the deployment of AMI systems, there are still millions of one-way devices currently deployed that cannot be practically replaced all at once. Moreover, in some environments and for some applications, cost pressures may encourage AMR system operators to deploy new one-way devices in lieu of more advanced and consequently more expensive two-way endpoint technologies. Simple sensor monitoring applications can also be added to utilize the transport infrastructure of the overlay 2-way AMI systems already deployed. This leaves AMR system operators with mixed systems in which one-way devices and two-way devices are operating in the same system, with each type of endpoint requiring a different reading process for collecting its data.
Moreover, given that 1-way devices may exist anywhere within the coverage footprint of a 2-way network, additional difficulties arise in such 2-way multi-hop networks where endpoints that are to act as relays for forwarding messages from one-way devices need to be specifically configured via a human-driven process, to support such operations. A practical solution is therefore needed to simplify and automate AMR system operations in mixed systems.